Two approaches to improve fertility of subclinical mastitic dairy cows

Abstract

Mastitis, particularly in its subclinical form, is a widely spread disease that reduces the fertility of lactating cows. A major cause of poor conception risk has been associated with delayed ovulation of a large subgroup of subclinical mastitic cows. This study examined 2 approaches to improve fertility in this subgroup. Subclinical mastitic cows were defined by somatic cell count elevated above a threshold of 150,000 cells/mL of milk determined in all monthly test day samples collected before AI. Uninfected (control) cows were defined by somatic cell count below threshold. In experiment 1, we examined a hormonal approach aimed to correct the timing of ovulation in mastitic cows in which it would otherwise be delayed. The probability of conception of mastitic and uninfected groups following Ovsynch (OVS) and timed AI versus AI following detected estrus (E) was examined (n=1,553 AI) and analyzed by a multivariable, logistic model statement using the GLIMMIX procedure of SAS. The OVS protocol significantly elevated the probability of conception of mastitic cows to a level similar to that of their uninfected counterparts. Actual mean conception risks for uninfected-E, subclinical-E, uninfected-OVS, and subclinical-OVS groups were 41.8, 26.4, 39.3, and 40.5%, respectively. The OVS protocol did not improve probability of conception in cows diagnosed with uterine disease postpartum. In experiment 2, a management approach aimed to better synchronize timing of ovulation with timing of AI in subclinical mastitic cows was examined. A second AI was added 24h after the first (routine) AI, following detection of natural estrus. Probability of conception did not differ between subclinical mastitic cows inseminated once or twice. Lack of improvement in conception risk might be related to low preovulatory LH surge in mastitic cows, which is likely to induce not only delayed ovulation but also disruption of oocyte maturation. Thus the OVS protocol can improve fertility of subclinical mastitic cows, probably due to "corrected" timing of ovulation in cows in which it would otherwise be delayed.

Comparing the effects of heat stress and mastitis on ovarian function in lactating cows: basic and applied aspects

“…The major finding was that "Ovsynch" increased conception in subclinical mastitic cows to rates similar to those in controls, whereas the conception rate of mastitic cows that were artificially inseminated after natural estrus remained low. Conception rates for uninfected-AI at estrus, subclinical-AI at estrus, uninfected-AI after "Ovsynch" and subclinical-AI after "Ovsynch" groups were 41.8%, 26.4%, 39.3%, and 40.5%, respectively [102]. Results suggested that the "Ovsynch" protocol can improve fertility of subclinical mastitic cows, most likely via synchronization of ovulation timing in cows in which it would otherwise be delayed.…”

“…Recently, a study aiming at improving fertility of subclinical mastitic cows was performed [101,102]. The assumption was that "correcting" the timing of ovulation in subclinical mastitic cows exhibiting delayed ovulation could improve their conception rate.…”

“…The assumption was that "correcting" the timing of ovulation in subclinical mastitic cows exhibiting delayed ovulation could improve their conception rate. The probability of conception was examined in subclinical mastitic and uninfected cows (n ¼ 1553) treated with the "Ovsynch" protocol and timed AI (first GnRH injection followed by PGF 2a 7 d later and a second GnRH injection 60 h later, and timed AI 16 h after GnRH), and compared with insemination after natural estrus [102]. The major finding was that "Ovsynch" increased conception in subclinical mastitic cows to rates similar to those in controls, whereas the conception rate of mastitic cows that were artificially inseminated after natural estrus remained low.…”

A 100-Year Review: Mastitis detection, management, and prevention

“…This research was followed by a study that identified similar detrimental effects for cows affected with subclinical mastitis during the early breeding period (Schrick et al, 2001). Since that time, numerous researchers have confirmed that even relatively modest levels of inflammation can affect fertility, and the effect of inflammation caused by mastitis beyond the mammary gland continues to be an important area of research (Lavon et al, 2011(Lavon et al, , 2016Hudson et al, 2012;Fuenzalida et al, 2015).…”

Optimization of the Estrus Synchronization Method and its Effect on Bulk Tank Milk Somatic Cell Count in Dairy Cattle Farming

“…McDougall and Voermans (2002) attributed the decrease in milk yield during estrus to an increased SCC level in goats when using two different estrus synchronization methods. Lavon et al (2016) reported pregnancy rates in cattle treated with the Ovsynch protocol that were similar to cattle without mastitis. Based on this finding, the Ovsynch protocol was proposed as a means of increasing fertility in cattle with subclinical mastitis.…”